Some espresso blends have extremely narrow temperature bands in which they perform well. In other words, they are fairly unforgiving. Lighter roasts, as you note, tend to be more acidic and, in my experience, require a higher brew temp (sometimes as high as 205F). The only underextraction issues I've ever experienced with a Linea has been due to a "cold nose" on the AVs (remedied by appropriate flushing) or over-dosing (which isn't necessarily sour). The sourness, to me, points to brew temp or too-light-of-a-roast. It is entirely possible that you just don't like those blends; there are plenty of well-known blends that I don't care for, for similar reasons).

Mitch,

Another simple test you can do is to grind finer and reduce the dose, or keep the same dose and let the shot run longer. Either way, the finer grind should give you a higher extraction yield and the espresso should taste less sour.

Similarly, you can try brewing the coffee in a drip, vac pot, french press, etc. See if you can get the extraction yield in the sweet spot with a reasonable balance between sour and bitter (ignore the flavor -- many espresso beans won't taste as intended by the roaster when brewed by other methods.) Like the first test, you can also try grinding finer and reducing the dose to see if you can push the extraction yield even higher. At some point, it'll top out.

The point of these tests is to determine if it's your espresso machine, the water or the beans (or a combination thereof.) If you can get a good extraction brewing the beans, then likely something is going on with your espresso machine. If not, then it's down to the water or the beans. The easy test there is to try different beans. Try darker roasts and try lighter roasts from other roasters.

I urge you to try these tests before your Strada arrives. I'd sure hate to see your face if the first pull on that machine is below 18% extraction yield!

Hopefully a happy day! I never brew any other coffee other than espresso but this morning as an experiment, I brewed a cup of regular coffee. Well, not one that anyone would want to drink but just as an experiment I ground 12 gm of espresso beans at normal espresso grind then added the grounds to the bottom of an empty coffee mug. I then added 197.2 gm of water from the brewhead of my Linea to the mug. I stirred and let it steep for 4 minutes. I then measured the TDS (using the espresso filter just in case) and it measured 1.47 giving me an extraction yield of 21.5%.

Based on the above experiment, I don't think water is my issue. The Linea must be the culprit. To be fair, I have modified the Linea with a PID and Piero cap so perhaps there are issues with these (although the PID shouldn't be any issue at all). Anyway, I excited about the new machine more than ever now.

just double-checking: what are your shot times & volumes?

barry wrote:just double-checking: what are your shot times & volumes?

I gather you are asking about pulling espresso shots. Those I start with the roaster's recommendations and move from there. This latest experiment was just to check extraction of coffee with water. I didn't use the machine other than to fill the mug with hot water.

I can't help but think that something very fundamental is being overlooked. I've been using Lineas on an almost daily basis for about 11 years, and worked with literally dozens and dozens of them, and know dozens more cafes and individuals that have used them, and continue to use them, without the issues you are attributing to your machine. That is not to say there isn't something wrong with *your* machine, but I think it says something about your speculation that the machine is designed to perform that way. It's not the PID or Piero caps, unless they were installed or configured improperly.

You said your shots are sour, and your extraction low. When asked about raising the brew temperature, you said the shots were sour & ashy, but you did not indicate what your measured extraction level was. Have you tried other (darker) blends, and what were the results? What is your brew pressure? Do you have a Scace I or Scace II on hand (I know you used one, but I don't know if you own one)? What are your typical shot times & volumes? I saw that at one point you tried bottled water, but did you completely drain and refill the brew boiler before resuming your measurements? I'm sorry if I'm asking you to repeat yourself, but I don't have time to wade through all the various threads on HB to assemble the bits & pieces.

As for your cup of coffee test, using a 4 minute dwell time with a coffee ground for espresso, will yield a higher than normal level of extraction.

It's not the PID or Piero caps, unless they were installed or configured improperly.

Since I installed and set up both of these, they are suspect

When asked about raising the brew temperature, you said the shots were sour & ashy, but you did not indicate what your measured extraction level was.

Roughly 17.5% No matter what I tried, I always got the same rough extraction yield except for one blend.

Have you tried other (darker) blends, and what were the results?

When I brewed Counter Culture's Toscano, I was able to get close to 19% yield. Those shots tasted good but that flavor profile is not what I enjoy. I prefer the lighter roasted SO with a lot of acidity.

Do you have a Scace I or Scace II on hand (I know you used one, but I don't know if you own one)?

I own a Scace I. I wish I had bought the Scace II as I would have been able to answer your next question...

What is your brew pressure?

If I can trust my internal gauge which is a replacement, I usually brew at 8.8 BAR. I have tried many pressures though. The other consideration is my Procon pump failed and I had to replace it with a Hydropure pump sold by EPNW.

I saw that at one point you tried bottled water, but did you completely drain and refill the brew boiler before resuming your measurements?

No, I didn't want to do that much work. I ran a gallon of bottled water through the system before I pulled any shots though.

What are your typical shot times & volumes?

Thanks for all your help Barry. Turns out my little experiment proves that my water is suspect. According to Vince Fedele my brew should have vastly over extracted. Now to learn about water formulators.

Before you throw money at the situation, why don't you actually test that theory? Try steeping espresso grounds in:
1) Fiji, or whatever water is recommended in the FAQ;
2) whatever water that you're normally using;
3) whatever water that you're normally using, but from the group.

Then test them to compare.

I'm gonna go with Occam's razor on this. Have you ever been able to pull a shot that you thought wasn't underextracted, on anybody's machine, anywhere?